A conventional powder-actuated fastening tool for thrusting anchors into hard cement wall or rock wall by means of explosive force produced by powders is shown in FIGS. 7 and 8, which is a substantially tubular tool and mainly includes a chamber tube 1a, a discharge tube 2a, a shell remover 3a, a sleeve 4a, a coupling 5a, an inner sliding block 6a, and a handle 7a. The chamber tube 1a is received in the discharge tube 2a, the discharge tube 2a has a front cover 21a and a rear cover 22a to substantially close two ends thereof, the shell remover 3a extends at one end into the chamber tube 1a and bears at a rear portion thereof an inner spring 31a, a limit nut 32a is screwed to a rear end of the shell remover 3a to prevent the inner spring 31a from moving out of the shell remover 3a and thereby limits the displacement range of the shell remover 3 a. The chamber tube 1a has a threaded rear end which extends out the rear cover 22a of the discharge tube 2a to engage with the coupling 5a so that the rear end of the shell remover 3a along with the inner spring 31a extends into the coupling 5a. An outer spring 33a is put over the inner spring 31a to enable the sleeve 4a to springily slide over the coupling 5a. A positioning slot 51a is provided at each side of the coupling 5a, and, pin holes 41a are provided on the sleeve 4a corresponding to the positioning slots 51a. A pin 42a is inserted into the pin hole 41a at one side of the sleeve 4a and extends through the internal sliding block 6a to fix the same in the hollow coupling 5a. When the sleeve 4a slides forward over the coupling 5a, it brings the sliding block 6a to move together so that the sliding block 6a may push the limit nut 32a screwed to the rear end of the shell remover 3a, causing the same to remove the shell in a longitudinal direction.
To operate such a conventional powder-actuated fastening tool, first insert a shaped powder 8a into a stepped hole at a front of the chamber tube 1a, then, position an anchor 9a having a ring 91a in a front inner hole of the chamber tube 1a, allowing a distance left between the hammering end of the anchor 9a and the shaped powder 8a. The ring 91a of the anchor 9a is fixedly attached to the anchor 9a and is used to seal the front opening of the chamber tube 1a so that the interior of chamber tube 1a forms a closed explosion chamber and to maintain the distance left between the anchor 9a and the powder 8a. When an anchor 9a is to be forced into a wall or other structural material, such as the light-weight steel frame below the ceiling, screw the handle 7a to the rear end of the above-described fastening tool, aim the anchor 9a at the desired spot, and make strenuous efforts to push the handle 7a, causing the anchor 9a to disengage from the ring 91a and shifts backward. When the hammering end of the anchor 9a contact the percussion cap of the powder 8a, the powder 8a explodes, and the explosive pressure so produced in the closed chamber of the chamber tube 1a pushes the anchor 9a in a reverse direction toward the wall or the target with a extremely big hammering force. When the anchor 9a is hammered into the wall or the target, the ring 91a shall be forced to a rear position near the hammering end of the anchor 9a.
There are several disadvantages existed in the conventional powder-actuated fastening tool and needing improvement:
1. The anchor 9a projects out of the front end of the chamber tube 1a. For the anchor 9a to disengage from the ring 91a and move back an adequate distance within an instantaneous moment, the user must keep the anchor 9a at an adequate launching distance from the wall or target and aim the anchor 9a at the desired spot and push the handle 7a instantaneously to hammer the anchor 9a in place. However, since there is a launching distance left between the anchor 9a and the wall, and the long handle 7a may not be always pushed steadily to precisely aim the anchor 9a at the target, the anchor 9a is frequently forced into a place deviated from the desired point and must be extracted from the wall and another anchor 9a must be hammered again. All of these cause waste in time, labor and material. The design thereof is not practical nor economical. PA1 2. The handle 7a must be strenuously pushed in an instantaneous moment so that the hammering end of the anchor 9a may contact the percussion cap of the shaped powder 8a to explode the powder 8a. The operation is laborious and inconvenient. PA1 3. The powder 8a can be used to hammer only one single anchor 9a each time. The user has to re-load the anchor 9a and shaped powder 8a each time an anchor 9a is hammered. The efficiency in using the conventional powder-actuated fastening tool is therefore very low. PA1 4. All the conventional powder-actuated fastening tools available in the market do not have muffler, and the loud noise from explosion during operation might have reverse influence on the living quality of area surrounding the working site, especially when the site is in the residential or school district.